Engine cooling device

ABSTRACT

A cooling device circulates cooling water through an engine main body and a radiator using an electric pump and supplies cool air to the radiator using an electric fan, thereby cooling the engine main body. During a dead soak period after an engine is shut off, a control unit controls the operation states of the electric pump and the electric fan on the basis of cooling water temperature detected by a water temperature sensor, outside air temperature detected by an outside air temperature sensor, and battery voltage. Specifically, when the engine is shut off, if it is determined on the basis of the cooling water temperature and the outside air temperature that the engine is in a high temperature state, the control unit controls the electric pump and the electric fan.

TECHNICAL FIELD

The present invention relates to an engine cooling device configured tocool an engine by circulating cooling water and more particularly to anengine cooling device configured to prevent an engine temperature riseafter the engine is stopped.

BACKGROUND ART

In a conventional engine, an amount of vapor to be generated in a fuelpipe increases due to a temperature rise during a dead soak periodfollowing stop of the engine, deteriorating restartability at hightemperatures and idle rotation stability. To enhance thehigh-temperature restartability of the engine, therefore, for example,Patent Document 1 listed below proposes a simple and low-cost enginecooling device capable of providing sufficient engine cooling effects.This device is arranged to operate an electric pump to circulate coolingwater in the engine, a radiator, and a heater to thereby cool theengine. The heater is provided with a cooling fan. Herein, an open/closevalve is placed somewhere in a cooling water passage connecting theradiator and the electric pump. For a predetermined time (during thedead soak) following the engine stop, the open/close valve is closed,while the electric pump and the electric fan are operated based onbattery voltage and engine water temperature to circulate the coolingwater only through the engine and the heater to cool the engine.

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: JP-A-2002-174120

Patent Document 2: JP-A-2007-170236

SUMMARY OF INVENTION Problems to be Solved by the Invention

Meanwhile, the cooling device in Patent Document 1 does not have anydefinite configuration about how to adjust the influence of outside airtemperature and the operations of the electric pump and the electricfan. Their conditions could not be set optimally. Accordingly, thefrequency of operation and the time (duration) of operation of theelectric pump and electric fan tend to increase. This may cause aproblem with battery deterioration.

Herein, an engine cooling performance of the cooling device isinfluenced by outside air temperature. It is therefore necessary to takea difference in outside air temperature into account. If the electricpump and the electric fan are operated uniformly, the electric power ofthe battery is apt to be excessively consumed, which may acceleratedeterioration of the battery. At a low outside air temperature, theelectric pump and the electric fan do not have to be operated uniformly.Thus, when an appropriate time lag is set between their operationtimings, efficient power consumption is enabled.

The present invention has been made in view of the circumstances tosolve the above problems and has a purpose to provide an engine coolingdevice capable of preventing battery deterioration during a dead soak ofan engine and also efficiently cooling the engine to enhancehigh-temperature restartability and idle rotation stability.

Means of Solving the Problems

(1) To achieve the above purpose, a first aspect of the inventionprovides an engine cooling device to cool an engine by operating anelectric pump to circulate cooling water in the engine and a radiatorand operating an electric fan to supply cooling air to the radiator, thecooling device including: cooling water temperature detecting means todetect a temperature of the cooling water; outside air temperaturedetecting means to detect a temperature of outside air; battery voltagedetecting means to detect a voltage of a battery for supplying electricpower to the electric pump and the electric fan; and control means tocontrol the electric pump and the electric fan during dead soakfollowing stop of the engine based on the temperature of the coolingwater detected by the cooling water temperature detecting means, theoutside air temperature of the outside air detected by the outside airtemperature detecting means, and the voltage of the battery detected bythe battery voltage detecting means.

According to the above configuration (1), during the dead soak followingthe engine stop, the electric pump and the electric fan are controlledby the control means based on the cooling water temperature and thebattery voltage and additionally based on the outside air temperature.When the outside air temperature is low, for example, the operation timeand the operation frequency of the electric pump and the electric fancan be limited by just that much.

(2) To achieve the above purpose, in the above configuration (1),preferably, the control means determines at the time when the engine isstopped whether or not the engine is in a high temperature state basedon the detected cooling water temperature and the detected outside airtemperature, and the control means operates the electric pump and theelectric fan when the engine is determined to be in the high temperaturestate.

According to the above configuration (2), in addition to the operationof the configuration (1), when the engine is determined to be in a hightemperature state based on the cooling water temperature and the outsideair temperature at the time of engine stop, the electric pump and theelectric fan are operated. When the engine is not determined to be inthe high temperature state, therefore, the electric pump and theelectric fan are not operated.

(3) To achieve the above purpose, in the above configuration (1) or (2),preferably, the control means operates the electric fan when thedetected outside air temperature is equal to or higher than apredetermined value, the detected cooling water temperature is equal toor higher than a predetermined value, and the detected battery voltageis equal to or larger than a first predetermined value.

According to the above configuration (3), in addition to the operationof the configuration (1) or (2), in a specific case where the outsideair temperature is equal to or higher than the predetermined value, thecooling water temperature is equal to or higher than the predeterminedvalue, and the battery voltage is equal to or higher than the firstpredetermined value, the electric fan is operated. Thus, the operationtime and the operation frequency of the electric fan can be limited.

(4) To achieve the above purpose, in one of the above configurations (1)to (3), preferably, the control means operates the electric pump whenthe detected outside air temperature is equal to or higher than apredetermined value, the detected cooling water temperature is equal toor higher than a predetermined value, and the detected battery voltageis equal to or higher than a second predetermined value.

According to the above configuration (4), in addition to the operationof one of the configurations (1) to (3), in a specific case where theoutside air temperature is equal to or higher than the predeterminedvalue, the cooling water temperature is equal to or higher than thepredetermined value, and the battery voltage is equal to or higher thanthe second predetermined value, the electric pump is operated. Thus, theoperation time and the operation frequency of the electric pump can belimited.

(5) To achieve the above purpose, in the above configuration (4),preferably, the control means operates the electric fan but does notoperate the electric pump when the detected outside air temperature isequal to or higher than the predetermined value, the detected coolingwater temperature is equal to or higher than the predetermined value,and the detected battery voltage is equal to or higher than a thirdpredetermined value smaller than the first predetermined value, thedetected battery voltage being less than the second predetermined value.

According to the above configuration (5), in addition to the operationof the configuration (4), in a specific case where the outside airtemperature is equal to or higher than the predetermined value, thecooling water temperature is equal to or higher than the predeterminedvalue, and the battery voltage is equal to or higher than the thirdpredetermined value but less than the second predetermined value, onlythe electric fan is operated. This can reduce battery power consumption.

(6) To achieve the above purpose, in one of the above configurations (3)to (5), preferably, the control means does not operate the electric pumpand the electric fan when at least one of conditions (a) to (c) isfulfilled; (a) the detected outside air temperature is less than thepredetermined value, (b) the detected cooling water temperature is lessthan the predetermined value, and (c) the detected battery voltage isless than a third predetermined value.

According to the above configuration (6), in addition to the operationof one of the configurations (3) to (5), in a specific case where atleast one of the conditions; the outside air temperature is less thanthe predetermined value, the cooling water temperature is less than thepredetermined value, and the battery voltage is less than the thirdpredetermined value, is fulfilled, both the electric pump and theelectric fan are not operated. This can reduce battery powerconsumption.

(7) To achieve the above purpose, in the above configuration (5),preferably, the control means stops the electric pump when the detectedbattery voltage becomes less than a fourth predetermined value smallerthan the second predetermined value while the electric pump and theelectric fan are operating.

According to the above configuration (7), in addition to the operationof the configuration (5), when the battery voltage becomes less than thefourth predetermined value lower than the second predetermined valuewhile the electric pump and the electric fan are operating, the electricpump is stopped. Thus, the cooling water is cooled by cooling air of theelectric fan in the radiator and battery power consumption is reduced.

(8) To achieve the above purpose, in the above configuration (7),preferably, the third predetermined value is smaller than the fourthpredetermined value.

(9) To achieve the above purpose, in one of the above configurations (1)to (8), preferably, the control means stops the electric pump and theelectric fan after a lapse of a predetermined post-stop time followingstop of the engine.

According to the above configuration (9), in addition to the operationof one of the configurations (1) to (8), since the electric pump and theelectric fan being operating after engine stop are stopped after a lapseof the post-stop time, there is no fear of the battery running out.

(10) To achieve the above purpose, in the above configuration (9),preferably, the control means calculates the post-stop time based on thedetected outside air temperature and the detected cooling watertemperature.

According to the above configuration (10), in addition to the operationof the configuration (9), the post-stop time is determined according todifferences in the outside air temperature and the cooling watertemperature.

(11) To achieve the above purpose, in one of the above configurations(1) to (10), preferably, the control means determines a request flowrate of the cooling water based on the detected cooling watertemperature and controls operation of the electric pump based on thedetermined request flow rate.

According to the above configuration (11), in addition to the operationof one of the configurations (1) to (10), the electric pump is operatedbased on the request flow rate corresponding to the cooling watertemperature.

Effect of the Invention

According to one of the configurations (1) to (4), it is possible toreduce power consumption of the battery during the dead soak of theengine, preventing deterioration of the battery, and efficiently coolthe engine. This can enhance high-temperature restartability of theengine and idle rotation stability.

According to the configuration (5), in addition to the effect of theconfiguration (4), it is possible to reduce unnecessary powerconsumption of the battery during the dead soak of the engine,preventing deterioration of the battery, and ensuring the life of thebattery. Furthermore, it is possible to cool the cooling water of theradiator and promptly circulate the relatively low-temperature coolingwater in the engine during high-temperature restart of the engine. Thus,the engine can be cooled rapidly.

According to the configuration (6), in addition to the effect of one ofthe configurations (3) to (5), it is possible to reduce unnecessarypower consumption of the battery during the dead soak of the engine,preventing deterioration of the battery, and ensuring the life of thebattery.

According to the configuration (7) or (8), in addition to the effect ofthe configuration (5), it is possible to reduce unnecessary powerconsumption of the battery during the dead soak of the engine,preventing deterioration of the battery, and ensuring the life of thebattery. Furthermore, it is possible to continuously cool the coolingwater of the radiator and promptly circulate the relativelylow-temperature cooling water during high-temperature restart of theengine. Thus, the engine can be cooled rapidly.

According to the configuration (9), in addition to the effect of one ofthe configurations (1) to (8), it is possible to avoid the engine fromentering a restart disabled state due to battery running out.

According to the configuration (10), in addition to the effect of theconfiguration (9), the electric pump and the electric fan do notcontinue to operate more than necessary during the dead soak. Thus,unnecessary power consumption of the battery can be reduced, therebypreventing deterioration of the battery, and ensuring the life of thebattery.

According to the configuration (11), in addition to the configuration ofone of the configurations (1) to (10), the electric pump does notoperate with a flow rate higher than necessary during the dead soak.This can reduce unnecessary power consumption of the battery, therebypreventing deterioration of the battery, and ensuring the life of thebattery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configurational diagram showing a cooling devicefor an engine in an embodiment;

FIG. 2 is a flowchart showing the details of a control program to beexecuted by a control unit in the embodiment;

FIG. 3 is a 3-D map showing a relationship between cooling watertemperature, outside air temperature, and fan drive request time in theembodiment;

FIG. 4 is a 3-D map showing a relationship between cooling watertemperature, outside air temperature, and pump drive request time in theembodiment;

FIG. 5 is a 2-D map showing a relationship between cooling watertemperature and pump drive request flow rate in the embodiment;

FIG. 6 is a graph showing a relationship between discharge electricquantity and battery life in the embodiment;

FIG. 7 is a time chart showing behaviors of various parameters in theembodiment;

FIG. 8 is a time chart showing behaviors of engine rotation speed,operations of an electric fan and an electric pump, temperature ofengine-parts, and battery voltage in the embodiment;

FIG. 9 is a graph showing variations in cooling water temperature withrespect to drive time of the electric fan and the electric pump in theembodiment, compared with a conventional example;

FIG. 10 is a graph showing variations in engine-parts temperature withrespect to drive time of the electric fan and the electric pump in theembodiment, compared with the conventional example; and

FIG. 11 is a graph showing variations in battery voltage with respect todrive time of the electric fan and the electric pump in the embodiment,compared with the conventional example.

MODE FOR CARRYING OUT THE INVENTION

A detailed description of a preferred embodiment of a cooling device ofan engine mounted in a vehicle, embodying the present invention will nowbe given referring to the accompanying drawings.

FIG. 1 is a schematic configurational view of the cooling device of theengine. This cooling device is arranged such that an electric pump 1 isoperated to circulate cooling water through an engine body 2 and aradiator 3, and electric fans 4 are operated to supply cooling air tothe radiator 3 to cool the engine body 2.

In the engine body 2, a water jacket 11 is provided to allow coolingwater to flow therethrough. This water jacket 11 includes an inlet 11 aand an outlet 11 b so that the cooling water flows in the engine body 2through the inlet 11 a, circulating through the engine body 2, and thenflows out of the engine body 2 through the outlet 11 a. The electricpump 1 is provided on the engine body 2 in correspondence with the inlet11 a. The outlet 11 b of the water jacket 11 is connected to an inlet 3a of the radiator 3 through a cooling water pipe 12. Furthermore, anoutlet 3 b of the radiator 3 is connected to a suction port of theelectric pump 1 through a cooling water pipe 13.

Accordingly, when the electric pump 1 is operated, the cooling water iscaused to circulate through the water jacket 11, then flowing out of thewater jacket 11 through the outlet 11 b into the radiator 3 via thecooling water pipe 12. The cooling water flowing in the radiator 3releases heat in the radiator 3, and then is sucked in the suction portof the electric pump 1 via the cooling water pipe 13 and discharged froma discharge port of the pump 1. The radiator 3 is provided with twoelectric fans 4. These electric fans 4 are operated to supply coolingair to the radiator 3.

At the outlet 11 b of the water jacket 11, a water temperature sensor 21corresponding to cooling water temperature detecting means is providedto detect the temperature of cooling water (cooling water temperature)THW. In the vicinity of the radiator 3, an outside air temperaturesensor 22 corresponding to outside air temperature detecting means todetect the temperature of outside air (outside air temperature) THA.

This cooling device includes a control unit 30 corresponding to controlmeans to control the electric pump 1 and the electric fans 4. To thecontrol unit 30, there are individually connected the electric pump 1,the electric fans 4, the water temperature sensor 21, and the outsideair temperature sensor 22. Further, an ignition switch (IG/SW) 23 and abattery 24 are also connected to the control unit 30. The control unit30 receives, from the water temperature sensor 21, a signal representingthe cooling water temperature THW at the outlet 11 b of the water jacket11. The control unit 30 receives a signal representing the outside airtemperature THA from the outside air temperature sensor 22. The controlunit 30 further receives signals related from engine start and enginestop from the IG/SW 23. A signal representing battery voltage GBA isalso input from the battery 24 to the control unit 30. The control unit30 corresponds to battery voltage detecting means to detect the batteryvoltage GBA.

The control unit 30 is configured to control the electric pump 1 and theelectric fans 4, during a dead soak period after the engine is stopped,based on the cooling water temperature THW detected by the watertemperature sensor 21, the outside air temperature THA detected by theoutside air temperature sensor 22, and the detected battery voltage GBA.To be concrete, the control unit 30 determines whether or not the enginebody 2 is in a high temperature state based on the detected coolingwater temperature THW and the detected outside air temperature THA atthe time of engine stop and, if determines that the engine body 2 is inthe high temperature state, activates the electric pump 1 and theelectric fans 4.

The details of the control program to be executed by the control unit 30to control the electric pump 1 and the electric fans 4 will be explainedbelow referring to a flow chart in FIG. 2.

In step 100, firstly, the control unit 30 determines whether or not theIG/SW 23 is turned OFF. If this determination result is negative, thecontrol unit 30 temporarily terminates subsequent processing. If thisdetermination result is affirmative, the control unit 30 advances theprocess to step 101.

In step 101, the control unit 30 reads the detected cooling watertemperature THW, outside air temperature THA, and battery voltage GBA.

In step 102, the control unit 30 calculates a fan drive request timeRTF. The control unit 30 performs this calculation by referring to a 3-Dmap using parameters; cooling water temperature THW, outside airtemperature THA, and fan drive request time RTF, as shown in FIG. 3. Inthis map, for example, if the outside air temperature THA is “45 (° C.)”and the cooling water temperature THW is equal to or higher than “105 (°C.)”, the fan drive request time RTF is “180 (sec)”.

In step 103, the control unit 30 calculates a pump drive request timeRTP. The control unit 30 performs this calculation by referring to a 3-Dmap using parameters; cooling water temperature THW, outside airtemperature THA, and pump drive request time RTP, as shown in FIG. 4. Inthis map, for example, if the outside air temperature THA is “45 (° C.)”and the cooling water temperature THW is equal to or higher than “105 (°C.)”, the pump drive request time RTP is “160 (sec)”.

In step 104, the control unit 30 calculates a pump drive request flowrate RFP. The control unit 30 executes this calculation by referring toa 2-D map using parameters; cooling water temperature THW and pump driverequest flow rate RFP as shown in FIG. 5. In this map, for example, ifthe cooling water temperature THW is equal to or higher than “105(°C.)”, the pump drive request flow rate RFP is “40 (L/m)”.

In step 105, the control unit 30 determines whether or not the outsideair temperature THA is equal to or larger than a predetermined valuetha1. For example, “35 (° C.)” may be applied to this predeterminedvalue tha1. If this determination result is affirmative, the controlunit 30 advances the process to step 106.

In step 106, the control unit 30 determines whether or not the coolingwater temperature THW is equal to or larger than a predetermined valuethw1. For example, “105 (° C.)” may be applied to this predeterminedvalue thw1. If this determination result is affirmative, the controlunit 30 advances the process to step 107.

In step 107, the control unit 30 determines whether or not the batteryvoltage GBA is equal to or larger than a first predetermined value bat1.For example, “11 (V)” may be applied to this first predetermined valuebat1. If this determination result is affirmative, the control unit 30advances the process to step 108.

In step 108, the control unit 30 determines whether or not a post-IGOFFtime TOF corresponding to a post-stop time is less than the fan driverequest time RTF. For example, “180 (sec)” may be applied to this fandrive request time RTF. If this determination result is affirmative, thecontrol unit 30 advances the process to step 109.

In step 109, the control unit 30 turns the electric fans 4 ON, therebysupplying cooling air to the radiator 3.

In step 110 following step 109, the control unit 30 determines whetheror not the battery voltage GBA is equal to or larger than a thirdpredetermined value bat3 smaller than the first predetermined valuebat1. For example, “10 (V)” may be applied to this third predeterminedvalue bat3. If this determination result is affirmative, the controlunit 30 advances the process to step 111.

In steps 105 to 108 and 110, on the other hand, if each determinationresult is negative, the control unit 30 turns the electric fans 4 OFF instep 116, thereby stopping supply of the cooling air to the radiator 3.

Thereafter, in step 111, the control unit 30 determines whether or notthe battery voltage GBA is equal to or larger than a secondpredetermined value bat2. If this determination result is affirmative,the control unit 30 advances the process to step 112. For example, “11(V)” may be applied to this second predetermined value bat2.

In step 112, the control unit 30 determines whether or not thepost-IGOFF time TOF is less than the pump drive request time RTP. Forexample, “160 (sec)” may be applied to this pump drive request time RTP.If this determination result is affirmative, the control unit 30advances the process to step 113.

In step 113, the control unit 30 turns the electric pump 1 ON, therebycirculating the cooling water through the engine body 2 and the radiator3.

In step 114, subsequently, the control unit 30 determines whether or notthe battery voltage GBA is less than a fourth predetermined value bat4.If this determination result is negative, the control unit 30 returnsthe process to step 112. If the determination result is affirmative instep 114, the control unit 30 advances the process to step 115. The sameapplies to the case where the determination results in steps 111 and 112are negative and the case where the process in step 116 is executed.

In step 115 following steps 111, 112, 114, and 116, the control unit 30turns the electric pump 1 OFF, thereby stopping circulation of thecooling water in the engine body 2 and the radiator 3, and temporarilyterminates subsequent processing.

In the above control, a lowest value of the battery voltage GBA is setto the third predetermined value bat3 (10 (V)) for the following reason.FIG. 6 is a graph showing a relationship between discharging electricquantity (Ah/Number of Times) and battery life (Year). To obtain thebattery life of “3 years”, it is found from this graph that thedischarging electric quantity has to be adjusted to “0.6 (Ah/Number ofTimes)”. As a precondition, the sum of the consumption power “100 (W)”of the electric fans 4 and the consumption power “20 (W)” of theelectric pump 1 is “120 (W)”. Assuming that the operation time of theelectric fans 4 and the electric pump 1 is at most “3 minutes (180seconds)” and the operating day of the same is “15 days”, therelationship with the battery voltage bat is established by thefollowing expression (1):

120 (W)÷bat (V)*3 (minutes)÷60≦0.6 (Ah)   (1)

This results in “bat ≧10 (V)” and reveals that a minimum battery voltageneeds to be “10 (V)”. In the present embodiment, therefore, the thirdpredetermined value bat3 of the battery voltage GBA is set to “10 (V)”corresponding to the minimum battery voltage.

Behaviors of various parameters according to the above control will beexplained below referring to a time chart in FIG. 7.

During warm-up running of a vehicle, when the cooling water temperatureTHW exceeds the predetermined value thw1, “105 (° C.)”, at time t1 asshown in FIG. 7( f), the pump drive request flow rate RFP is set to “40L” as shown in FIG. 7( b). This value is determined by referring to themap shown in FIG. 5. Further, the fan drive request time RTF is set to“180 (sec)” and the pump drive request time RTP is set to “160 (sec)”,respectively. Those values are determined by referring to the maps shownin FIGS. 3 and 4.

Thereafter, when the IG/SW 23 is turned OFF at time t2 as shown in FIG.7( a), the engine is stopped and the engine rotation speed NE becomes“0” as shown in FIG. 7( j). Furthermore, the outside air temperature THAis the predetermined value tha1 (“35 (° C.)”) or higher as shown in FIG.7( i), the cooling water temperature THW is the predetermined value thw1(“105 (° C.)”) or higher as shown in FIG. 7( f), and the battery voltageGBA is the predetermined value bat1 (“11 (V)”) as shown in FIG. 7( e).Thus, the electric fans 4 are turned ON to start operating as shown inFIG. 7( d). Since the electric fans 4 are ON and the battery voltage isthe second predetermined value bat2 (“11 (V)”) or higher as shown inFIG. 7( e), the electric pump 1 is turned ON to start operating as shownin FIG. 7( c).

Subsequently, at time t3, the post-IGOFF time TOF becomes the pump driverequest time RTP (e.g., “160 (sec)”) or more as shown in FIG. 7( h), theelectric pump 1 is turned OFF to stop operating as shown in FIG. 7( c).

Furthermore, at time t4, the post-IGOFF time TOF becomes the fan driverequest time RTF (e.g., “180 (sec)”) or more as shown in FIG. 7( h), theelectric fans 4 are turned OFF to stop operating as shown in FIG. 7( d).

When the IG/SW 23 is then turned ON at time t5 as shown in FIG. 7( a),the engine starts up as shown in FIG. 7( j), increasing the enginerotation speed NE. A period from time t2 to time t5 is a dead soakperiod as shown in FIG. 7.

Herein, in a conventional example, as indicated by a thick line in FIG.7( a) and broken lines in FIG. 7( b) to (g), during the dead soak afterthe IG/SW is turned OFF, an electric pump and an electric fan areoperated at the same timing and for the same duration and a pump requestdrive flow rate is determined depending on situations. Thus, the batteryvoltage GBA relatively sharply falls off, the cooling water temperatureTHW relatively slowly decreases, and the temperature of each part of theengine (engine-parts temperature) relatively sharply rises.

On the other hand, in the present embodiment, as indicated by thicklines in FIG. 7( a) to (g), during the dead soak after the IG/SW 23 isturned OFF, the pump drive request flow rate RFP is determined based onthe cooling water temperature THW obtained at that time. Further, theelectric pump 1 and the electric fans 4 are simultaneously operated, andthen, the electric pump 1 is stopped first and the electric fans 4 arestopped slightly later. Accordingly, the battery voltage GBA relativelyslowly decreases, the cooling water temperature THW relatively rapidlydecreases, and the engine-parts temperature relatively slowly rises.

In the present embodiment, specifically, as shown in a time chart inFIG. 8, during the dead soak of the engine, the drive times of theelectric fans 4 and the electric pump 1 are controlled, so that theengine-parts temperature can be kept lower and the battery voltage canbe held higher than those in the conventional example. FIG. 9 is a graphshowing variations in cooling water temperature THW with respect to thedrive time of the electric fans 4 and the electric pump 1, compared withthe conventional example. This graph reveals that the cooling watertemperature THW in the present embodiment more rapidly decreases than inthe conventional example. FIG. 10 is a graph showing variations inengine-parts temperature with respect to the drive time of the electricfans 4 and the electric pump 1, compared with the conventional example.This graph reveals that the engine-parts temperature in the presentembodiment more rapidly decreases than in the conventional example. FIG.11 is a graph showing variations in battery voltage GBA with respect tothe drive time of the electric fans 4 and the electric pump 1, comparedwith the conventional example. This graph shows that the battery voltageGBA in the present embodiment more slowly decreases than in theconventional example.

According to the engine cooling device in the present embodimentexplained above, during the dead soak after the engine is stopped, theelectric pump 1 and the electric fans 4 are controlled by the controlunit 30 based on the outside air temperature THA in addition to thecooling water temperature THW and the battery voltage GBA. Accordingly,if the outside air temperature THA is low, the operation time and theoperation frequency of the electric pump 1 and the electric fans 4 arelimited by just that much. To be concrete, in the specific case wherethe outside air temperature THA is equal to or higher than thepredetermined value tha1, the cooling water temperature THW is equal toor higher than the predetermined value thw1, and the battery voltage GBAis equal to or higher than the first predetermined value bat1 and equalto or higher than the second predetermined value bat2, the electric pump1 and the electric fans 4 are operated. Thus, limitations can be imposedon the operation time and the operation frequency of the electric pump 1and the electric fans 4. This makes it possible to reduce powerconsumption of the battery 24 during the dead soak of the engine,preventing deterioration of the battery 24, and to efficiently cool theengine body 2, thereby enhancing the high-temperature restartability andthe idle rotation stability of the engine. According to the coolingdevice in the present embodiment, specifically, it is possible to bothprevent deterioration of the battery 24 and enhance the high-temperaturerestartability and the idle rotation stability of the engine.

According to the engine cooling device in the present embodiment, at thetime of engine stop, when the engine body 2 is determined to be in ahigh temperature state based on the cooling water temperature THW andthe outside air temperature THA, the electric pump 1 and the electricfans 4 are operated. Thus, when the engine body 2 is not determined tobe in the high temperature state, the electric pump 1 and the electricfans 4 are not operated. Accordingly, power consumption of the battery24 can be reduced during the dead soak of the engine, thereby preventingdeterioration of the battery 24. Also, the engine body 2 can beefficiently cooled, thereby enhancing the high-temperaturerestartability and the idle rotation stability of the engine.

According to the engine cooling device in the present embodiment, in thespecific case where the outside air temperature THA is equal to orhigher than the predetermined value tha1, the cooling water temperatureTHW is equal to or higher than the predetermined value thw1, and thebattery voltage GBA is equal to or higher than the third predeterminedvalue bat3 smaller than the first predetermined value bat1, but thebattery voltage GBA is less than the second predetermined value bat2,only the electric fans 4 are caused to operate. Thus, power consumptionof the battery 24 is reduced. This can reduce unnecessary powerconsumption of the battery 24 during the engine dead soak, therebypreventing deterioration of the battery 24, and ensuring the life of thebattery 24. Furthermore, the cooling water in the radiator 3 can becooled during the dead soak of the engine, so that the relativelylow-temperature cooling water is allowed to promptly circulate in theengine body 2 during high-temperature engine restarting, thus rapidlycooling the engine body 2.

According to the engine cooling device in the present embodiment, in thespecific case where at least one of the conditions is fulfilled; theoutside air temperature THA is less than the predetermined value tha1,the cooling water temperature THW is less than the predetermined valuethw1, and the battery voltage GBA is less than the third predeterminedvalue bat3, both the electric pump 1 and the electric fans 4 are notoperated. Thus, power consumption of the battery 24 is reduced. Thisalso can reduce unnecessary power consumption of the battery 24 duringthe dead soak of the engine, thereby preventing deterioration of thebattery 24, and ensuring the life of the battery 24.

According to the engine cooling device in the present embodiment, whilethe electric pump 1 and the electric fans 4 are operating, when thebattery voltage GBA becomes less than the fourth predetermined valuebat4 smaller than the second predetermined value bat2, the electric pump1 is stopped. Thus, the cooling water is cooled by the cooling air fromthe electric fans 4 in the radiator 3 and also power consumption of thebattery 24 is reduced. This can reduce unnecessary power consumption ofthe battery 24 during the dead soak of the engine, thereby preventingdeterioration of the battery 24, and ensuring the life of the battery24. It is further possible to continuously cool the cooling water in theradiator 3 and promptly circulate the relatively low-temperature coolingwater in the engine body 2 during high-temperature engine restarting,thereby rapidly cooling the engine body 2.

According to the engine cooling device in the present embodiment, theelectric pump 1 and the electric fans 4 being operating after enginestop are stopped after a lapse of the post-IGOFF time TOF following theengine stop. Thus, there is no fear that the battery runs out. In thisregard, it is possible to avoid the engine from entering a restartdisabled state due to battery running out.

According to the engine cooling device in the present embodiment, theaforementioned post-IGOFF time TOF is determined according to thedifferences in outside air temperature THA and cooling water temperatureTHW. Therefore, the electric pump 1 and the electric fans 4 do notcontinue to operate more than necessary during the dead soak andunnecessary power consumption of the battery 24 can be reduced, thuspreventing deterioration of the battery 24, and ensuring the life of thebattery 24.

According to the engine cooling device in the present embodiment, thepump drive request flow rate RFP is determined based on the coolingwater temperature THW and thus the electric pump 1 is operated based onthe pump drive request flow rate RFP according to the cooling watertemperature THW. Therefore, the electric pump 1 is not operated at aflow rate higher than necessary during the dead soak. This can reduceunnecessary power consumption of the battery 24, thereby preventingdeterioration of the battery 24, and ensuring the life of the battery24.

The present invention is not limited to the aforementioned embodimentand may be embodied in other specific forms without departing from theessential characteristics thereof.

For instance, in the above embodiment, the electric fans 4 are two.Alternatively, a single electric fan or three electric fans may beprovided.

In the above embodiment, the first predetermined value bat1 and thesecond predetermined value bat2 related to the battery voltage GBA areset to the same value “11 (V)”, but may be set to different values fromeach other.

INDUSTRIAL APPLICABILITY

The present invention is utilizable in a vehicle engine, for example.

REFERENCE SIGNS LIST

-   1 Electric pump-   2 Engine body-   3 Radiator-   4 Electric fan-   11 Water jacket-   12 Cooling water pipe-   13 Cooling water pipe-   21 Water temperature sensor (Cooling water temperature detecting    means)-   22 Outside air temperature sensor (Outside air temperature detecting    means)-   24 Battery-   30 Control unit (Control means, Battery voltage detecting means)

1. An engine cooling device to cool an engine by operating an electric pump to circulate cooling water in the engine and a radiator and operating an electric fan to supply cooling air to the radiator, the cooling device including: cooling water temperature detecting means to detect a temperature of the cooling water; outside air temperature detecting means to detect a temperature of outside air; battery voltage detecting means to detect a voltage of a battery for supplying electric power to the electric pump and the electric fan; and control means to control start and stop, and operation time of each of the electric pump and the electric fan during dead soak following stop of the engine based on the temperature of the cooling water detected by the cooling water temperature detecting means, the outside air temperature of the outside air detected by the outside air temperature detecting means, and the voltage of the battery detected by the battery voltage detecting means.
 2. The engine cooling device according to claim 1, wherein the control means determines at the time when the engine is stopped whether or not the engine is in a high temperature state based on the detected cooling water temperature and the detected outside air temperature, and the control means operates the electric pump and the electric fan when the engine is determined to be in the high temperature state.
 3. The engine cooling device according to claim 1, wherein the control means operates the electric fan when the detected outside air temperature is equal to or higher than a predetermined value, the detected cooling water temperature is equal to or higher than a predetermined value, and the detected battery voltage is equal to or larger than a first predetermined value.
 4. The engine cooling device according to claim 1, wherein the control means operates the electric pump when the detected outside air temperature is equal to or higher than a predetermined value, the detected cooling water temperature is equal to or higher than a predetermined value, and the detected battery voltage is equal to or higher than a second predetermined value.
 5. The engine cooling device according to claim 4, wherein the control means operates the electric fan but does not operate the electric pump when the detected outside air temperature is equal to or higher than the predetermined value, the detected cooling water temperature is equal to or higher than the predetermined value, and the detected battery voltage is equal to or higher than a third predetermined value smaller than the first predetermined value, the detected battery voltage being less than the second predetermined value.
 6. The cooling device engine according to claim 3, wherein the control means does not operate the electric pump and the electric fan when at least one of conditions (a) to (c) is fulfilled; (a) the detected outside air temperature is less than the predetermined value, (b) the detected cooling water temperature is less than the predetermined value, and (c) the detected battery voltage is less than a third predetermined value.
 7. The engine cooling device according to claim 5, wherein the control means stops the electric pump when the detected battery voltage becomes less than a fourth predetermined value smaller than the second predetermined value while the electric pump and the electric fan are operating.
 8. The engine cooling device according to claim 7, wherein the third predetermined value is smaller than the fourth predetermined value.
 9. The engine cooling device according to claim 1, wherein the control means stops the electric pump and the electric fan after a lapse of a predetermined post-stop time following stop of the engine.
 10. The engine cooling device according to claim 9, wherein the control means calculates the post-stop time based on the detected outside air temperature and the detected cooling water temperature.
 11. The engine cooling device according to claim 1, wherein the control means determines a request flow rate of the cooling water based on the detected cooling water temperature and controls operation of the electric pump based on the determined request flow rate. 